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Over the past three decades, the bed bug Cimex lectularius has resurged as a prominent indoor pest on a global scale. Knockdown-associated insecticide resistance (kdr) involving the voltage-gated sodium channel, targeted by organochlorine and pyrethroid insecticides, was first reported in C. lectularius within a few years of the widespread use of dichlorodiphenyltrichloroethane (DDT) and has been implicated as a significant factor contributing to the species’ recent resurgence. Since then, selection with pyrethroid insecticides has intensified, yet little is known regarding its short-term impacts on the frequency of kdr-associated mutations. Here, we report temporal changes in the frequencies of three kdr-associated mutations in C. lectularius populations collected across the USA from two time periods, sampled approximately a decade apart. The results reveal a significant increase in the frequencies of kdr-associated mutations over this period and the absence of the insecticide-susceptible genotype in recent collections. Furthermore, a significant transition was observed toward infestations possessing multiple kdr-associated mutations. These findings suggest that the persistent use of pyrethroid insecticides over the past decade continues to impose strong selection pressure on C. lectularius populations, driving the proliferation of kdr-associated mutations. They demonstrate that, if unabated, strong anthropogenic selection can drive the rapid evolution of adaptive traits.
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This content will become publicly available on March 1, 2026
Assessing Temperature-Dependent Deltamethrin Toxicity in Various kdr Genotypes of Aedes aegypti Mosquitoes
Insecticide resistance surveillance systems for vector-borne diseases are crucial for early detection of resistance and the implementation of evidence-based resistance management strategies. While insecticide susceptibility bioassays are typically conducted under controlled laboratory conditions, mosquitoes in the field experience varying environmental conditions, with temperature being a key determinant. Understanding the relationship between temperature and insecticide toxicity is essential for interpreting and extrapolating assay results across different climate zones or more locally across days with different weather conditions. In this study, we examined Aedes aegypti mosquitoes with different genetic backgrounds of insecticide resistance. Mosquitoes were homozygous for the knockdown resistance (kdr) F1534C mutation, plus either (1) homozygous for the kdr 1016V wildtype allele, (2) homozygous for the kdr V1016I mutant allele, or (3) heterozygous genetic crosses. These three genotypes were exposed to deltamethrin using WHO tube tests at three temperatures (22 °C, 27 °C, and 32 °C) and varying dosages. LC50 values were determined for each genotype and temperature combination. A negative temperature coefficient was observed exclusively in female mosquitoes homozygous for the 1016V wildtype allele, indicating reduced pyrethroid toxicity at higher temperatures. No temperature–toxicity relationship was found in males of this genotype or in other genotypes of either sex. These findings suggest that temperature may interact with kdr mutations and possibly even sex, highlighting the complex interactions between genetic mutations and environmental factors, such as temperature, in determining the insecticide resistance phenotype. Given the wide distribution of Ae. aegypti, understanding how local climate conditions influence insecticide performance will help improve control strategies and slow resistance evolution, protecting public health efforts against mosquito-borne diseases
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- Award ID(s):
- 2047572
- PAR ID:
- 10621906
- Publisher / Repository:
- Insects
- Date Published:
- Journal Name:
- Insects
- Volume:
- 16
- Issue:
- 3
- ISSN:
- 2075-4450
- Page Range / eLocation ID:
- 254
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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Abstract BackgroundInsecticide resistance in malaria vectors can be spatially highly heterogeneous, yet population structure analyses frequently find relatively high levels of gene flow among mosquito populations. Few studies have contemporaneously assessed phenotypic, genotypic and population structure analysis on mosquito populations and none at fine geographical scales. In this study, genetic diversity, population structure, and insecticide resistance profiles ofAnopheles funestusandAnopheles arabiensiswere examined across mosquito populations from and within neighbouring villages. MethodsMosquitoes were collected from 11 towns in southern Mozambique, as well as from different neighbourhoods within the town of Palmeira, during the peak malaria transmission season in 2016. CDC bottle bioassay and PCR assays were performed withAnophelesmosquitoes at each site to determine phenotypic and molecular insecticide resistance profiles, respectively. Microsatellite analysis was conducted on a subsample of mosquitoes to estimate genetic diversity and population structure. ResultsPhenotypic insecticide resistance to deltamethrin was observed inAn. funestussensu stricto (s.s.) throughout the area, though a high level of mortality variation was seen. However, 98% ofAn. funestus s.s.wereCYP6P9ahomozygous resistant.An. arabiensiswas phenotypically susceptible to deltamethrin and 99% werekdrhomozygous susceptible. BothAnophelesspecies exhibited high allelic richness and heterozygosity. Significant deviations from Hardy–Weinberg equilibrium were observed, and high linkage disequilibrium was seen forAn. funestus s.s.,supporting population subdivision. However, the FSTvalues were low for both anophelines (− 0.00457 to 0.04213), Nmvalues were high (9.4–71.8 migrants per generation), AMOVA results showed almost 100% genetic variation among and within individuals, andStructureanalysis showed no clustering ofAn. funestus s.s.andAn. arabiensispopulations. These results suggest high gene flow among mosquito populations. ConclusionDespite a relatively high level of phenotypic variation in theAn. funestuspopulation, molecular analysis shows the population is admixed. These data indicate thatCYP6P9aresistance markers do not capture all phenotypic variation in the area, but also that resistance genes of high impact are likely to easily spread in the area. Conversely, other strategies, such as transgenic mosquito release programmes will likely not face challenges in this locality.more » « less
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Abstract In recent years, bed bugs have experienced a remarkable resurgence on a near global scale. While reports have primarily focused on the common bed bug, Cimex lectularius (L.), which has resurged largely in temperate regions, in tropical regions the tropical bed bug, Cimex hemipterus (F.) (Hemiptera: Cimicidae), has reemerged as well. Recent reports of C. hemipterus introductions to subtropical and temperate regions, outside of the species natural distribution, suggest the potential for establishment and further spread. Establishment may be aided by insecticide resistance mechanisms, such as the presence of knockdown resistance (kdr)-associated mutations, which potentially confer resistance to pyrethroid, pyrethrin, and organochloride insecticides. Here, we present the first report of the detection and likely establishment of C. hemipterus in Honolulu, Hawaii, from samples collected in 2009 and 2019. Furthermore, through partial sequencing of the voltage-gated sodium channel, we report the presence of kdr-associated mutations in all samples. These findings have implications for the implementation of control strategies aimed at eradicating infestations.more » « less
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